1. Field of the Invention
The present invention relates generally to electrodes for electrical stimulation of heart muscle tissue, and more particularly to an epicardial electrode assembly at the distal end of a pacing lead which is adapted to be connected to a cardiac pacemaker.
2. Description of the Prior Art
A cardiac pacemaker is operable to deliver pacing electrical impulses to an electrode in contact with a heart muscle for ventricular stimulation of the muscle. The electrode is attached to the interior endocardium or the exterior epicardium of the heart muscle, and connected via a flexible pacing lead to the pacemaker which is surgically implanted under the patient's skin.
Typically, an epicardial electrode assembly includes a small electrode body of a flexible silicone rubber. An electrode contact is molded into the rubber body of the electrode assembly and the electrode assembly is sutured to the heart wall using conventional suturing methods.
In order for the surgeon to perform the suturing of the epicardial electrode assembly to the heart muscle in accordance with a conventional method, a thoracotomy is usually required in order to gain access to the heart. The sutures in time cause growth of fibrosis around the electrode assembly which is undesirable since the fibrous tissue reduces the effectiveness of the contact electrode, and in general, the conventional method causes more trauma to the heart than is desirable.
Heretofore various proposals have been made for attaching an electrode assembly to heart muscle in a manner which is faster and with less trauma than prior methods.
For example, the Hess U.S. Pat. No. 4,144,890 discloses a contact device having pointed prongs that are spaced apart from the electrode contact and inserted into the epicardiac wall for securing the device.
The Hess U.S. Pat. No. 4,066,085 discloses a contact device having prong like attaching members with barbs for attaching to the epicardiac wall.
The Rockland U.S. Pat. No. 4,010,758 discloses a bipolar electrode comprising a helix-shaped electrode to be screwed into the heart tissue.
The Rosenbauer U.S. Pat. No. 3,814,104 discloses a unipolar hollow electrode for attachment to a heart having wire hooks that, before attachment, are contained inside the electrode, and during attachment are exposed, extended and penetrate the epicardiac tissue.
The Tachick U.S. Pat. No. 3,472,234 discloses a body organ electrode having a stiff helical member that is screwed into the heart tissue.
The Wesbey U.S. Pat. No. 3,244,174 discloses a body implantable conductor for a pacemaker of bipolar construction with sharply pointed curved electrodes for insertion into the epicardial tissue.